No completion certificate held
Thames Water says it holds no completion, handover or commissioning certificate for the capacity scheme.
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Environmental information response · 10 September 2026
What Thames Water answered, and what remains unresolved
We asked nineteen questions about Bourton-on-the-Water sewage treatment works. The response contains useful evidence, but most questions remain unresolved.
Covering note
A useful disclosure, but an incomplete response
Thames Water responded on 10 September 2026 to our Environmental Information Regulations request.
The response includes some useful information. However, most of our nineteen questions remain unresolved.
The clearest answer confirms that Thames Water holds no completion, handover or commissioning certificate for the capacity scheme.
A supplied delay register forecasts construction completion in October 2027. Formal takeover is forecast for February 2028. This differs sharply from the published expectation of autumn 2026. The project was originally due for completion in 2023.
Other responses supplied different documents or data from those requested. Several questions received no direct answer. Two refusals cited no EIR exception or public-interest assessment.
The detailed record separates our questions, Thames Water's answers and SBSG's analysis. Readers can examine the evidence and reach their own conclusions.
3Clearly answered
7Partly answered, contradictory or misdirected
7Not answered
2Refusals challenged
These are SBSG's editorial categories. They are not legal findings or official determinations.
Four findings that matter
A much later forecast
The delay register forecasts October 2027 construction completion and February 2028 takeover.
The wrong discharge data
The supplied level readings are not the requested event records. Their relationship to the public record is unclear.
Overflow target moved
Thames Water described a shift towards 2045–2050. It supplied no supporting decision record.
Question by question
The complete review, in manageable sections
Open any question to compare Thames Water's response with our assessment and next question.
Capacity scheme and completion
1.1Current flow-to-full-treatment capacityNot answered
What Thames Water said
Thames Water described permitted values and final-effluent quality. It did not state the works' current flow-to-full-treatment capacity.
SBSG assessment
The response does not answer the question asked.
Why it matters
The capacity available today affects when storm overflow may occur.
1.2Programme for the capacity schemePartly answered
What Thames Water said
Thames Water supplied programme L956.02, which concerns the phosphorus scheme.
SBSG assessment
The supplied programme does not appear to be the requested capacity-scheme programme.
Why it matters
A programme is needed to test published completion claims.
1.3Completion, handover and commissioning certificatesClearly answered
What Thames Water said
Thames Water states that it holds no completion, handover or commissioning certificates.
SBSG assessment
This directly answers the records question. It does not establish whether any element is already operating.
Why it matters
No supplied certificate demonstrates formal completion of the capacity scheme.
1.4Revisions to the completion programmeClearly answered
What Thames Water said
A delay register shows earlier February 2024 dates. It forecasts construction completion on 15 October 2027 and takeover on 29 February 2028. It records 109 early warnings and 23 maximum-risk items. An SSEN power diversion is identified as the main driver.
SBSG assessment
The register provides a valuable history of delay. Its dates differ sharply from the published autumn 2026 expectation.
Why it matters
The latest supplied forecast is years later than the original March 2023 target.
Phosphorus scheme and the meaning of completion
2.1Regulatory basis for phosphorus reductionNot answered
What Thames Water said
Thames Water referred to a national statutory target and a future limit of 0.4 milligrams per litre.
SBSG assessment
No WINEP reference, driver code or permit condition was supplied.
Why it matters
The formal obligation determines both the required outcome and its deadline.
2.2Phosphorus programme datesPartly answered
What Thames Water said
Thames Water said the 0.4 milligrams-per-litre limit applies by March 2030. Its programme gives benefit delivery on 30 May 2030. The same material shows an Ofwat regulatory date of 31 March 2028.
SBSG assessment
The three dates are not reconciled.
Why it matters
Readers cannot judge programme compliance without one clear regulatory date.
3.1How Thames Water defines completionPartly answered
What Thames Water said
Thames Water said several schemes remain active. It said each has its own completion criteria, but supplied no criteria.
SBSG assessment
The response gives context but withholds the definition requested.
Why it matters
Different meanings of completion can create misleading public dates.
3.2Completion dates communicated externallyPartly answered
What Thames Water said
Thames Water said no external completion date had been communicated and no relevant records were held.
SBSG assessment
That statement appears inconsistent with published GISMP dates, Thames Water's autumn 2026 webpage, and the supplied delay register.
Why it matters
Public statements should match internal programme evidence.
Discharge data, amendments and volume
4.1Raw event-duration-monitoring recordsPartly answered
What Thames Water said
Thames Water supplied 122,612 sewer-level readings. These are not the requested discharge-event records. The series also contains gaps, including about 573 hours in 2023 and 48 hours in 2025.
SBSG assessment
The dataset may concern a different combined-sewer-overflow asset. Its relationship to the public Bourton STW record is unclear.
Why it matters
Event records are needed to check starts, stops and retrospective changes.
4.2Method for deriving discharge start and stop timesNot answered
What Thames Water said
Thames Water linked to Defra guidance and described general quality checks. It said data is recorded at 15-minute intervals.
SBSG assessment
No Thames Water algorithm or validation process was supplied. Some provided readings occur at one-minute or two-minute intervals.
Why it matters
The calculation method matters when published stop times later appear different.
4.3Procedure for retrospective amendmentsRefusal challenged
What Thames Water said
Thames Water described the procedure briefly but said the detailed document was for internal use only.
SBSG assessment
The response cites no EIR exception and includes no public-interest assessment.
Why it matters
A transparent amendment process protects trust in the public discharge record.
4.4Audit trail for altered event recordsNot answered
What Thames Water said
Thames Water said no spurious activations or exclusion labels were recorded in 2026.
SBSG assessment
That does not answer whether stop times were amended or whether an audit log exists.
Why it matters
An audit trail would allow observed changes to be checked fairly.
5.1Measurement or estimation of discharge volumePartly answered
What Thames Water said
Thames Water said discharge volumes and quality are not monitored. It added that there is no regulatory requirement to monitor them.
SBSG assessment
The answer does not address whether volumes are estimated or modelled. The discharge point discussed is also unclear.
Why it matters
Duration alone cannot show the quantity or concentration released.
Infiltration, overflow targets and funding
6.1Infiltration work completed since January 2024Clearly answered
What Thames Water said
Thames Water referred to the GISMP appendices. It said no further infiltration work had been completed since publication in November 2025.
SBSG assessment
This provides a direct answer to the period covered.
Why it matters
Groundwater infiltration can consume sewer capacity and increase overflow pressure.
6.2Evidence for claimed infiltration reductionsNot answered
What Thames Water said
Thames Water supplied a narrative description but no calculation, model, report or verification record.
SBSG assessment
The basis for the stated 35 per cent and 50 per cent reductions remains untested.
Why it matters
Percentage claims need evidence if they influence future investment decisions.
7.1GISMP update cyclePartly answered
What Thames Water said
Thames Water said the last GISMP update was November 2025 and updates are annual. It did not give the next publication date.
SBSG assessment
The answer also refers to the second Drainage and Wastewater Management Plan cycle, without confirming Bourton's future reporting route.
Why it matters
A clear update timetable lets the community track commitments and change.
7.2Basis for the revised storm-overflow targetNot answered
What Thames Water said
Thames Water described a shift from 2035–2040 to 2045–2050.
SBSG assessment
No supporting decision record, analysis or programme document was supplied.
Why it matters
Moving the target by about a decade requires a clear evidential basis.
8.1AMP8 and PR24 funding allocationNot answered
What Thames Water said
Thames Water supplied a programme whose cost columns contain zero values.
SBSG assessment
No budget line or funding value was provided.
Why it matters
A programme without visible funding cannot be assessed confidently.
8.2Funding beyond AMP8Refusal challenged
What Thames Water said
Thames Water declined to provide information because later funding had not been agreed with regulators.
SBSG assessment
The response cites no EIR exception and includes no public-interest assessment.
Why it matters
The answer should distinguish between information not held and information being withheld.
Underlying record
Read the full analysis
The Word document contains every question, Thames Water's summarised response and our full analysis. It was prepared after SBSG reviewed the four supplied attachments.